My baby is 6 months old and she have this lump under her colar bone. We think its a cysts. What should we do?

Its getting bigger I think, and a little pink/red. I'm worry that she has to go into surgery. She's only 6 months old..
Update: I took her to the doctor and he gave her a big bottle of cephalexin but its not helping. I'm just really worry.
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